let lessons = [
	{title: '媒体查询响应式布局',category: 'css'},
  	{title: 'FLEX 弹性盒模型',category: 'css'},
	{title: 'MYSQL多表查询随意操作',category: 'mysql'}
];


const hd = ["houdunren", "hdcms"];
const keys = hd.keys();
console.log(keys.next());
console.log(keys.next());

for(let k of hd) {
	console.log(k)
}

console.log('-----------------------\n')
var it = hd.keys()
console.log(it)
console.log(it.next());
console.log(it.next());

// console.log(it.hasNext())

console.log('-----------------------\n')
var it = hd.keys()
while (({ value, done } = it.next()) && done === false) {
	console.log(value, done);
}
